Hydroentanglement or “spunlacing” is a process used for mechanically bonding a web of loose fibers to form fabrics directly from fibers. Fabrics formed by the hydroentanglement process typically belong to those in the nonwovens' family of engineered fabrics. The underlying mechanism in hydroentanglement is the subjecting of the fibers to a non-uniform pressure field created by a successive bank of high-velocity water jets. The impact of the water jets with the fibers, while they are in contact with their neighbors, displaces and rotates the fibers with respect to their neighbors and entangles the same with neighboring fibers. During these relative displacements, some of the fibers twist around and/or inter-lock with neighboring fibers to form a strong structure based upon frictional forces between the fibers touching one another. The final outcome of the hydroentanglement process is a highly compressed and uniform fabric composed of entangled fibers. These structures are highly flexible, yet are very strong and outperform their woven and knitted counterparts in many measures of performance. The process is a high-speed low-cost alternative to other methods of producing fabrics wherein typical hydroentangling machines can run as fast as 700 meters or more per minute and are typically 1 to 6 meters wide. The process owes its success to the peculiar properties of coherent high-speed water jets.
Various patents have issued that are directed to the hydroentangling process in general and several have attempted to solve the serious problem of nozzle erosion that is inherent with high water pressures. U.S. Pat. No. 3,033,721 is directed to a method and apparatus for producing foraminous fabrics from a layer of fibrous material such as a fibrous web wherein the individual fiber elements are capable of movement under the influence of an applied fluid force. U.S. Pat. No. 4,805,275 is directed to a method of producing nonwoven fabrics through a treatment with high velocity water streams wherein a fibrous web is treated on a water impermeable supporting member with water jet streams ejected from a nozzle. The nozzle disclosed in the '275 Patent is a cone-capillary nozzle (i.e., cone-up nozzle) which results in a non-constricted water jet with minimal effective breakup length. U.S. Pat. No. 6,668,436 is directed to a method of treating sheet material using pressurized waterjets wherein a perforated plate with inserts made of zirconia, sapphire, ruby or other materials of equivalent hardness are used to increase the life of the nozzles. The inserts disclosed in the '436 Patent suffer from inherent design and machining problems that lower their efficiency and raise operating costs.
Therefore, it would be advantageous to employ a composite hydroentangling nozzle strip that could be subjected to the extremely high pressures found in today's hydroentangling machines without failing due to premature erosion of the nozzle inlet edge. It would also be advantageous to employ a composite hydroentangling nozzle strip that could withstand the erosion properties of cavitation while allowing a constricted water jet to form within the nozzle assembly. Finally, it would be advantageous to utilize a composite hydroentangling nozzle strip that can be easily and cost effectively maintained by the end user.